OF PEAS AND PUPS
PART V
MUTATIONS
The duplicating
properties of the Chromosomes and Genes are of considerable consistency. This
consistency makes the application of the laws of heredity practical.
Occasionally, as with all things, there is a slip-up. A gene 'GOOFS' OR 'IS
GOOFED' by some quirk....by some chemical change.....When this happens a
MUTATION is said to have taken place. It is the sudden abrupt change in a gene
from one Allelic Form to another. It is not necessarily accompanied by an
"explosion" as indicated in figure 22.
Most Mutations are
recessive and harmful. When a mutation takes place in a Germ Cell (a FUNCTIONAL
SPERMATOZOON OR OVUM) it follows heredity trails. Since Recessives must usually
come in pairs to show, it may be generations before finding a mate...either of
its own making or the same mutation which developed in another animal of the
same species....It differs from a "throw back" in that the new gene
was not formerly in the breed. Even, a Dominant Mutation may not make itself
known since its effect may range from lethal to zero.
Horns in cattle are
normal...hornless or polled a Mutation. The stubby legs of the badger-digging
Dachshund are thought to be of mutant origin and dominant. The wirelike hair of many breeds is thought to have resulted
from a mutation and I too, is dominant. In this latter
regard, we do not infer that the GWP was once a GSP one of whose w's mutated to W. A guess would be that the mutation
occurred in some early dog species, possible now extinct and probably not too
remote from the wolf.
The practical value to
the dog breeder for his awareness of mutations is limited; however, should you
have a Shorthair Pup, pop up without dew claws or with his tail naturally the
proper length, DON'T drown him....Platinum in mink was the first of the
mutation mink to handsomely reward their breeders with gold. it
arose as a recessive (in the
Mutations occur
constantly in nature but at a rather slow rate; one popping up somewhere in
100,000 to 1,000,000 gene generations. In spite of this more than 600 mutations
are known in the fruit fly alone but many of them have been artificially
produced for study....Artificially they may be induced by radiation, extreme
temperature changes, chemical agents and the like.
Mutations which produce
great and obvious changes...wirehair, stubby legs, polled cattle...are few and
far between. I know of no such in the GSP. Yet at the rate that mutations are
known to take place many have occurred in our breed "since Hektor was a pup" (HEKTOR 1, VOL.1, GSP STUDBOOK
WHELPED 1886). It is altogether possible that as a result of mutations in many
minor genes, the cumulative effects may have been more significant to the breed
than is realized. After discussing the qualitative characteristics in Part V!, it may become obvious how this could be possible. many of the great changes wrought by nature through the ages
have come about by these minute variations at these tremendous odds. Among
bacteria which may produce a new generation in a matter of minutes, mutations
are more obvious. Their interest to man and beast rests not alone in their
demonstration of evolutionary processes but more especially in their practical
effects.
Let assume that you or
your pup, have a bacterial infection. That an antibiotic has
been prescribed to be taken over a five day period. By the second day
much improvement is noted and the medication stopped. On the fourth day, the
condition returns and medication is resumed...but this time the condition does
not improve. What has happened? The bacteria are now resistant to that drug. A
MUTANT STRAIN HAS DEVELOPED.
In the laboratory it is
possible to develop (breed) strains which can resist concentrations of
antibacterial agents many times stronger than those which would kill the
original strain. This is accomplished by gradually increasing the concentration
until a mutation has occurred which thrives in this environment. When this
strain becomes well established the concentration is again increased,
presenting this new strain with circumstances under which they barely survive
until another mutation develops which thrives in this newer environment. This
process is continued until it can be pushed no farther or until resistance to
the desired concentration has been reached....It is interesting that the
mutated strain will not survive under the original circumstances. it is not surprising, however, since it is improbable that
many animals on earth today, including man, could survive the living conditions
which existed when they first appeared on the early geologic horizon.
Basically, this is the process of evolution and since evolving a better
Shorthair is our goal, there is a message here.....
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If
the "bacteria breeder" (we are all bacteria breeders, like it or
not) sets as his goal or ideal an "animal" which lives, multiplies
and flourishes in a specific environment, he reaches that goal by gradual
scientifically planned steps, which the dog breeder would do well to emulate.
both breeders are using variations for progress. The
"steps" graphing the progress of the bacteria breeder might look
something like this...(Figure 23) |
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The
dog breeder, on the other hand, usually presents a graph which looks more
like the Down-Jones averages...not very constant or rapid, with many
set-backs but still, one which always shows some progress over the long
haul...(Figure 24) |
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Why crawl when you can
run? Means are available, if we will but use them, to push progress at three at
three or four times its present rate. The dog breeder will more closely match
the steady upward advance of the bacteria breeder if he, too, sets a definite
and positive goal and makes specific step by step plans to reach that goal. if he line breeds to the best until something better comes
along and then line breeds to that. WE will have more to say about that later.
HYBRID VIGOR
Unfortunately, we have
all seen Weimaraner-Shorthair and/or lab-Shorthair
crosses. Often they are fine rugged looking animals with considerable natural
ability in the field. Such cross-breeding exhibits what is called HYBRID VIGOR
OR HETEROSIS. The F1's are superior to either P1. The
mule which results from the crossing of horse and as is the classical example
of this phenomenon. Their vigor is historic, yet,
they are rarely fertile....Corn production has greatly increased by the use of
hybrid seed. The seed results from the crossing (hybridizing) of two strongly
inbred strains of corn. The benefits of the hybrid seed fall off sharply in
subsequent generations. "Nik-chiks", a
trade name, for a line of baby chicks, are strong, disease resistant, fast
growing, heavy-meated birds, which are produced by
this genetic process. The only way to get more "chicks which
'nicked'" is to repeat the original crossings which produced the first
ones. They cannot reproduce themselves...The same genetic mechanism which is
thought to produce this HETEROSIS functions in the same manner within a breed.
The results are not often quite so drastic since the genetic differences are
not quite so diverse.
The three terms, HYBRID
VIGOR, HETEROSIS AND NICKING are often used interchangeably. The results are
that the offspring are superior to the parents. Whatever improvements, is for
the F1 only, it contributes little to overall breed improvement. it is thought that each parent has some gaps in their double
genetic necklace. When the strands are separated at MEIOSIS (FIG 7 REDUCTION
DIVISION) and rejoined in fertilization, the recessive leaks o fth one, are filled by the dominant plugs of the other, so
that no Double Recessives exist to fault the Phenotype. Although not completely
understood, the genetic picture is thought to look much like....(Figure
25)
The pups have no chance
of reproducing their own excellence...breed them and see.....They will slip
right back into the trough of mediocrity with their parents, if they do not
slip over the edge and drop down into the gutter. Such pups,
must be most carefully assayed before breeding. The diversity of their origins
should raise serious suspicions as to their prepotency..."NICKING"
can, and usually does, present the same genetic picture, yet it could present a
picture like FRANZ (the black beads are considered incomplete
dominants)..(Figure 26)
ERBA AND EIFER 'NICKED'
TO PRODUCE FRANZ. He is better than either of them. No Hybrid vigor or Heterosis can account
for him. he is not HYBRID-anything or
HETERO-anything...He is Homozygotic dominant. He is
therefore inbred and prepotent. FLOR is not superior
to her parents Phenotypically
or Genotypically. I have failed to find in the
literature a discussion of the differences which may exist in these three
terms. I submit that the difference illustrated is one and, although rare, can
exist. Another is this...the improvement of pups over parents can be the result
of an Epistatic effect (A gene that alters either
direction or intensity of another gene) which is not thought to be the case in
Hybrid Vigor or Heterosis. Epistasis, as we have said, is not well understood. We will
have to await further knowledge of individual gene action. When and if such
knowledge does become available, it may lend further impetus to the breeding
which follows. Meanwhile, DO NOT be led astray by the
all-knowing character who maintains that knowledge of individual gene action is
essential to the practical use of Mendelism. THE
IGNORANCE OF SUCH A ONE DOES A GREAT DISSERVICE TO BREED BETTERMENT.
REVERSION
THROW BACK. ATAVISM AND
REVERSION REFERS TO THE APPEARANCE IN A PUP OF SOME HEREDITARY CHARACTERISTIC
WHICH DOES NOT APPEAR IN THE PARENTS AND MAY NOT HAVE APPEARED IN THE BREED OR
STRAIN FOR MANY GENERATIONS......Like the smoothhair
which is said to occasionally crop up among Wirehairs. Long considered some
mysterious trick of fate, Father Mendels
gift of knowledge makes it all clear now....in fact, there is no reasonable
explanation without that knowledge....
Recessives must come in
pairs to show. A single recessive (like a mutation) may ramble through the
generations for ages before finding a mate, particulary
if that specific gene is rare in the breed. The longer it remains hidden, of
course, the less likely it is to ever come to the surface. Even if fate joins a
sire and dam each carrying the same recessive, it will show up only once out of
four pups and in an individual mating it might not even show up at all....If
"Aa" and "Aa"
did mate and not show an "aa" pup, they
would scatter enough "a's" around that you
can rest assured that they would pop up sooner or later and probably
sooner....Recessives are always at the root of these throw backs. Usually it is
a Double recessive, as above, occasionally a single. A Single Recessive acting
with an incomplete dominant "Aa" can
produce an effect not present in either parent, "AA" or "aa"....:Aa" pups cannot
breed true but must be reproduced each time by "AA" - "aa" parents, while "AA" and "aa" pups will duplicate themselves with ease. This
merely demonstrates again the importance of Genetic Purity....HOMOZYGOSIS.
GENE FREQUENCY
As the name implies
GENE FREQUENCY refers to how often a specific gene appears, or is present, in a
give population, in a particular breed. One member of an Allelic pair may be rarer
or more abundant than its partner. The gene for liver, E, in the GSP has
frequency of 1, because it is present in every member of the breed, as is the K
for short hair. If the gene for black, B, is no longer present in the breed,
that gene has a frequency of 0-. If there are still some blacks in the breed,
as we hear-tell, then the B is not zero, but approaching it....The frequency of
the recessives which might produce Throw-Backs are approaching that "goose
egg". The appearance of a black Shorthair from non-black parents is
naturally, an impossibility. If you see such a one you
can be sure that both parents were not Shorthairs...contrary to what the guy
says....
The object of the game
is to increase the Frequency of Desirable Genes to 1, where they will stay
(barring a mutation) and to decrease the Frequency of the undesirable genes to
zero, where they too will stay, HOMOZYGOSIS, the greatest single factor for
gene betterment, presents genes with no other frequency than 1.0.
PREPOTENCY
The purpose of this
series is to stimulate thought as well as to inform. With this in mind, read
carefully the following....A DOG NEED NOT BE INBRED TO BE GREAT, BUT HE MUST BE
INBRED TO BE A GREAT SIRE.....Repeat...."HE MUST BE INBRED TO BE A GREAT
SIRE" - TO BE PREPOTENT.....
This may call for a
reversal of our thinking, yet it is fact not fantasy. Such a statement will be
challenged only by one who has made No Effort to understand the workings of the
genetic system; or one who considers the pedigree the sole guide to dog
breeding. We shall discuss it in more detail under "Relationship" and
"Breeding Plans" which will follow later.
Returning to our
"beads for genes", we find two pups with pretty near the same
ability...the same Phenotype. ARTIG is a great dog, a great sire and
inbred....AXEL is also a great dog, but a poor sire and is outbred.
When we say one is inbred and the other outbred we
are not looking at any pedigrees, we are looking at the Genotype....the only
positive way to know what we are doing...we are looking at our beads for
genes... (Figure 27)
THE PURPOSE OF INBREEDING, is to bring like gens
from the male and female Gametes to the zygote. In so far as this is
accomplished, inbreeding has take place...pedigrees to the contrary
notwithstanding. So ARTIG is inbred even though his sire and dam are no closer
related, in the pedigree, than fourth cousins twice removed by marriage. AXEL
is outbred though his father and mother be half-sibs.
PREPOTENCY is the
ability of an animal (sire or dam) to stamp its seal upon its offspring...TO
CAUSE THE PUPS TO LOOK AND/OR ACT MORE LIKE THE PREPOTENT PARENT THAN THE OTHER
PARENT.....Although prepotency for dominant faults is
possible, we shall consider only prepotency for good
here...the mechanism is the same in both cases. The prepotent
sire can contribute more to the breed than can the prepotent
dam, merely because of the difference in the reproductive potentials of male
and female. It can be rightly said, however, that a prepotent
bitch, properly handled, can offer more to the breed than the greatest sire
ever whelped...handled as most such sires are handled....Still thought to be
some mysterious quirk by many, prepotency is today
pretty well understood by geneticists and thoughtful breeders everywhere. There
are two prime factors involved...Dominance and Homozygosity....Both
factors can be controlled by the genetic tools available to the average
breeder. These tools are selection and inbreeding...Both tools are without
value, in building or maintaining prepotency, if they
are not used together. We will have more to say about them in a future installment.
PREPOTENCY is a matter
of Homozygous Dominance...it is therefore, also a matter of degree, COMPLETE
PREPOTENCY IS IMPOSSIBLE. Complete Homozygosity is
next to impossible (Remember 103000) and complete dominance, even if possible,
is not desirable in the GSP. Complete prepotency for
good is impossible because some of our desirable characteristics are Recessive
and No Animal can stamp another with a recessive trait, good or bad. "It
takes two to Tango." We often hear how some outstanding specimen of the
breed passed his prepotency on to his sons, grandsons
or even his great grandsons. It sounds good, it makes a great story, BUT, it
has no basis in fact. Think! Are we going back to the old "sire only"
theory? PREPOTENCY IS NOT HEREDITARY....IT CANNOT BE TRANSFERRED FROM PREPOTENT
PARENT TO OFFSPRING....The prepotent characteristics are passed on to the pups, sure, because it takes only one
dominant to show. But it takes Two Dominants for Prepotency.
Single Dominants would show up in but half the pups in F2, if there were no
Inbreeding....PREPOTENCY IS THE ABILITY TO TRANSMIT. IT IS NOT THE VIRTUES
THEMSELVES. So, the sons of the prepotent sire did
not receive any Homozygosity from him. If indeed they
are Homozygous, he gave his full measure, one-half, and their dam
"nicked" with him to supply the other half. No parent however prepotent or homozygous can contribute more than a single
gene to any Allelic Pair!
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ARTIG
(meaning good, well-mannered) is prepotent for
these six genes (out of 10,000 pair). ZART (meaning frail or fragile) is a
genetic blank (for these genes). This is an Outbreeding,
a Hybridization because it brings Unlike Genes
together in the fertilized egg. (Figure 28) DAX
AND DAGMAR are prepotent. They were built by
line-breeding (inbreeding) to ARTIG who is prepotent.
Inbreeding the "D" litter would make prepotency
heredity because BOTH parents are prepotent...homozygous
dominant, and this is a pretty rare occurrence. The homozygosity
is a long difficult condition to evolve. Once built, it can be totally
wrecked in one outbreeding. No one would claim,
least of all this author, that prepotency is as
easily built or so simply maintained, as Figure 28 would indicate, yet, this
is the process....This is exactly, the way the genes operate, AND this is
exactly the way the genes must be held together, if the breed is to gain. Take
BANNING in F1 (Fig. 28) and breed here to AXEL (Fig. 27), then breed that F2
to a gene string of your own imagination. Do a little crossing over, if you
wish. See how rapidly that pretty black double strand necklace of ARTIG'S
goes to pot.....Not also, how the outbreeding of
ARTIG to ZART diminished his homozygosity to zero.
The dominance is still there but the homozygosity
is gone.....Restoring it is not easy. |
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These is only one way
to build homozygosity and that is through
Inbreeding....The longer inbreeding is continued or the closer the Genetic
Relationship of the mates; the greater the Homozygosity.
Greater homozygosity means greater prepotency....Of course it goes without saying that it is
necessary to start with Superior Genetic Material. The most reliable guide to
the prepotency of any individual, before breeding, is
his COEFFICIENT OF INBREEDING (FX). This figure gives us the probable
percentage of homozygosity, above the breed average,
for that individual. We will explain how this figure is obtained and give its
practical value in the section of this series covering "Breeding
Plans".
It is often said, in
fact we have said in this series, that it makes no difference to whom the prepotent sire is bred all his puppies will be great. This
is stretching a point. The prepotent sire, because he
is not completely homozygous, will usually produce better pups, and pups which
probably possess a greater degree of prepotency
themselves, when he is mated with a superior bitch of his own strain, than when
he is mated to an equally superior bitch from another strain. It is a matter of
degree. The pure bred dog will be prepotent over the
mongrel.
Usually the prepotent sire is bred far and wide, but rarely is any
thought given to returning his daughters and granddaughters to him for
service....Most times, when these fine pups have reached mating age, their
owners study with great diligence their pedigrees....WHY IS THIS CAREFUL STUDY
APPLIED? Simply, to be sure that no animal on it will be used as a sire, Oh,
they are not all like that. Some, the bolder ones, might dare to select a male,
sight unseen, from the fifth or sixth generation of that pedigree. And, if the
pups turn out poorly they'll blame it on inbreeding degeneration. The fact of
the matter is this...."RAPID PROGRESS IN ANIMAL BREEDING WILL HAVE TO WAIT
ON THE INTELLIGENT USE OF INBREEDING" BREEDING & IMPROVEMENT IN FARM
ANIMALS, Rice & Andrews (McGraw-Hill NYC 1951)
Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 | Part 8 | Part 9 | Part 10 | Part 11 | Part 12 | Part 13 | Part 14 | Corrections to Part 12 & 13
Copyright 2001. Dr. James G. McCue, Jr. All rights
reserved. Postscript: And his legacy lives on in the German
Shorthaired Pointers of today. May they
always be healthy and bred with forethought and planning.
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